Arsenic is a metalloid with similar properties to phosphorus. Arsenic oxidizes to form hygroscopic, colorless, odorless As2O3 and As2O5. The principal means of arsenic dispersion through nature is via water, and varies from locations based on soil and arsenic forms.
Arsenic has been attributed to changes in respiratory, gastrointestinal, hematopoietic, and cardiovascular systems. Because of the similarities between arsenic and phosphorus, arsenic can substitute in place of phosphorus in some biological reactions, making it poisonous. Particularly, consumption of arsenic-contaminated water may enter the metabolic citric cycle, inhibiting succinate dehydrogenase and preventing ATP production. Arsenic poisoning is cumulative and symptoms include nausea, vomiting, stomach aches, diarrhea, and delirium. Ingested arsenic is deposited into fingernails and skin Further, arsenic can remain in hair follicles for years following the arsenic exposure.
Bangladesh, India, and Nepal have experienced a massive epidemic from arsenic groundwater contamination. 35 million people are believed to be consuming water with at least 50 μg/L, and 57 million people drinking water with at least 10 μg/L of arsenic. Nongovernmental organizations entered the region and established tube wells to collect groundwater and prevent the indigenous populations from using bacteria-contaminated surface water. Over 8 million wells were built since the program began in the 1970s. Roughly one quarter of Bangladesh's population now rely on water collected from tube-wells for drinking. However, testing has revealed one in five of the tube wells are contaminated by water containing ten to fifty times the arsenic levels considered safe by the World Health Organization.
Most plant species produce an exopolysaccharide, a polymer of mono- and polysaccharides and proteins bonded by glycosidic bonds, referred to as mucilage. Plants secrete the substance to slow water loss, aid germination, and store food.
The tuna cactus (Opuntia ficus indica) mucilage produced by the flattened pads of this cactus was of particular interest. It can easily be recognized by its green, thick long pads, one linked to the next. The nopal plants are very inexpensive to cultivate and edible. Nopal pads are formed of complex carbohydrates that have the ability to store and retain water, allowing these plants to survive in extremely arid environments. Nopal mucilage is a neutral mixture of approximately 55 high-molecular weight sugar residues composed basically of arabinose, galactose, rhamnose, xylose, and galacturonic acid and has the capacity to interact with metals, cations and biological substances.
Mucilage is used in producing agar and used as an adhesive Importantly, mucilage swells in water but is insoluble. As such, the substance has the potential to precipitate ions, bacteria and particles from aqueous solutions. Further, the material has unique surface active characteristics, making it an ideal candidate for enhancing dispersion properties, creating emulsifications, and reducing surface tension of high polarity liquids.